In the space of about 750 years, native forest cover has been reduced from 85% of the land area (23 million hectares) to about 23% (6.2 million hectares).
Most of New Zealand’s lowland forests, wetlands, dunes and estuaries have been converted into pasture or towns, with original ecosystems reduced to a patchwork of isolated fragments.
Pasturelands and exotic forests
Before people, about 5% of New Zealand’s land area was grassland. Today, grass covers more than 38% of New Zealand’s total land area – 52% of the North Island and 29% of the South Island. Pastureland is not good kiwi habitat.
Exotic forests are a mixed blessing for kiwi – birds can be at risk when land is cleared for planting, but kiwi do live in established plantation forests.
In 2006, planted forest was estimated to cover 1.8 million hectares of New Zealand’s total land area. However, since the dairying boom began, fewer exotic forests are being replanted and some immature forest is being converted to dairy pasture. This could turn out to be bad for kiwi.
The impact of clearing land
Land clearance affects kiwi in three main ways:
- They can be killed when land is cleared by burning, and by the large rollers used to crush vegetation.
- It concentrates kiwi and their predators into smaller areas.
- The kiwi’s social organisation is affected. Kiwi are ferociously territorial. Less habitat means more competition for space, more boundary wars, less breeding, and more birds pushed out into farmland where they can fall foul of dogs.
Thankfully kiwi are adaptable, and live in a huge range of habitats – from native forest and scrub to rough farmland and plantation forests, sand dunes and snowy tussocks, even mangroves. They especially like places where stands of trees run down to rivers and include pockets of wetland vegetation.
Because they are soil feeders, kiwi prefer places where they can get straight to the dirt, rather than having to probe through the thick leaf litter of a forest floor. They dislike places trampled by livestock because the ground is compacted.
Kiwi can survive quite well when predators are controlled, enough shelter and feeding places are left and the ground is not too dry or compacted.